High interfacial compatibility nanosilica composite polymer electrolyte, preparation method and application thereof

Abstract

The application belongs to the technical field of batteries, and discloses a high-interface-compatibility nano-silicon dioxide composite polymer electrolyte, a preparation method and application thereof, and the preparation method comprises the following steps: providing a trimethoxy (3,3,4,4,5,5,6,6,6-nonafluorohexyl) silane hydrolysate; adding polyvinylidene fluoride and an organic solvent into the trimethoxy (3,3,4,4,5,5,6,6,6-nonafluorohexyl) silane hydrolysate, and then adding butanedinitrile and lithium salt to obtain a front solution of the composite polymer electrolyte; and coating the front solution of the composite polymer electrolyte into a film through scraping and drying. The nano-silicon dioxide composite polymer electrolyte is uniform and consistent as a whole, has high interface compatibility, and the assembled full battery still maintains 100% coulomb efficiency and a capacity close to 150 mAh / g after 200 cycles, and has high capacity retention rate and stable charge-discharge cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a highly interfacially compatible nano-silica composite polymer electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium metal batteries have become a research hotspot in the battery field due to their high energy density and other advantages. Among them, the development of polymer electrolytes is considered to be the main way to effectively solve the problems of flammability, easy leakage and poor temperature stability of liquid electrolytes, and has become the key to designing and manufacturing high-energy lithium batteries.

[0003] Polymer electrolytes are a class of solid-state materials that use specific polymers as a matrix to dissolve lithium salts and achieve ion transport. They possess unique flexibility, electrochemical stability, and ease of processing. Currently, commonly used polymer electrolyte matrices include polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, and polyvinylidene fluoride (PVDF). Among these, although PVDF is not an ion-conducting polymer, it has attracted widespread attention due to its high electrochemical stability and stability with metallic lithium. Traditional PVDF electrolytes generally suffer from low room-temperature ionic conductivity and poor mechanical properties. Current methods mainly focus on introducing inorganic fillers into the polymer matrix to reduce polymer crystallinity and construct an organic / inorganic interface to achieve lithium ion adsorption and guided transport, thereby improving the ionic conductivity and thermal stability of the electrolyte. For example, patent application 202510169344.3 discloses a bismuth halide-polyvinylidene fluoride composite solid electrolyte membrane for high-energy-density batteries and its preparation method. This method introduces bismuth halide into a PVDF substrate to achieve uniform interaction between bismuth halide as a filler and PVDF, thereby improving the overall electrochemical performance of the battery.

[0004] In the process of realizing this invention, the inventors discovered that the prior art has at least the following problems: Inorganic particles as fillers often have the defect that the particles are easy to agglomerate and cannot be uniformly dispersed in the matrix. Although the performance of the electrolyte membrane can be improved by constructing multi-dimensional inorganic particles as fillers, such as metal chloride salts in the form of nanoflowers, it is difficult to maintain the high specific capacity of the full battery for long cycles. In addition, the performance of inorganic particle composite electrolytes is relatively simple and difficult to cope with complex application scenarios. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a nano-silica composite polymer electrolyte with high interfacial compatibility, its preparation method, and its applications. It specifically solves the defect of poor interfacial compatibility in PVDF electrolytes. The preparation method yields a nano-silica composite polymer electrolyte that is uniformly homogeneous, without obvious pores or agglomeration, and exhibits high interfacial compatibility. Full cells assembled with this nano-silica composite polymer electrolyte retain 100% coulombic efficiency and a capacity close to 150 mAh / g after 200 cycles, demonstrating high capacity retention and stable charge-discharge cycle performance. Pouch cells assembled with this nano-silica composite polymer electrolyte can stably drive external loads.

[0006] Compared with the prior art, the present invention has the following advantages:

[0007] 1. The method for preparing a high interfacial compatibility nano-silica composite polymer electrolyte of the present invention includes blending a trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate with polyvinylidene fluoride (PVDF) to obtain a pre-solution of the composite polymer electrolyte. This method can achieve uniform dispersion of monodisperse silica in PVDF. At the same time, the long fluorocarbon chain formed by 3,3,4,4,5,5,6,6,6-nonafluorohexyl in trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane can interact with PVDF, showing high compatibility with PVDF and enhancing the interfacial stability and mechanical properties of the electrolyte membrane.

[0008] 2. The nano-silica composite polymer electrolyte of the present invention has high compatibility and a wide electrochemical window, and can be adapted to high-voltage cathodes. The full cell assembled with the nano-silica composite polymer electrolyte still maintains 100% coulombic efficiency and a capacity of nearly 150 mAh / g after 200 cycles, exhibiting high capacity retention and stable charge-discharge cycle performance. The pouch battery assembled with the nano-silica composite polymer electrolyte can stably drive external loads and can cope with complex battery application scenarios.

[0009] 3. The preparation method of the nano-silica composite polymer electrolyte of the present invention is reliable in principle, simple to operate, and conducive to industrial production.

[0010] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the full battery assembled in Example 1;

[0012] Figure 2 This is a schematic diagram of the structure of the full cell assembled in Comparative Example 1;

[0013] Figure 3 This is a schematic diagram showing the electrochemical test results of the full cells of Example 1 and Comparative Example 1 at 0.5C rate at room temperature;

[0014] Figure 4 This is a schematic diagram showing the ionic conductivity test results of the SS / SS coin cell composed of CPE-PVDF|FSCA in Example 1.

[0015] Figure 5 This is a schematic diagram showing the test results of the lithium-ion transference number of the battery composed of CPE-PVDF|FSCA in Example 1;

[0016] Figure 6 Here is a SEM image of CPE-PVDF|FSCA from Example 1;

[0017] Figure 7 The image shows the SEM image of CPE-PVDF|SiO2 in Comparative Example 1.

[0018] Figure 8 This is a schematic diagram illustrating the physical demonstration of how a CPE-PVDF|FSCA-constructed pouch cell drives external components in Example 1. Detailed Implementation

[0019] The technical solution will now be clearly and completely described with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] In the following description, the term "and / or" is used to describe the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural.

[0021] In the following description, the terms “including,” “containing,” “having,” and “containing” are open-ended terms, meaning that they include but are not limited to.

[0022] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0023] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] The technical principle employed in this invention is as follows: The performance of the PVDF electrolyte is improved by blending trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate with a polyvinylidene fluoride (PVDF) electrolyte matrix. Monodisperse silica is highly dispersed in PVDF, and the long fluorocarbon chains interact with PVDF, enhancing the interfacial compatibility of the PVDF composite polymer electrolyte and resulting in a full battery with higher electrochemical performance.

[0026] On the one hand, a method for preparing a nano-silica composite polymer electrolyte with high interfacial compatibility is provided, comprising:

[0027] Hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane is provided;

[0028] Polyvinylidene fluoride (PVDF) and an organic solvent are added to the hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane, followed by the addition of succinate and lithium salt to obtain a pre-solution of the composite polymer electrolyte. The mass of the organic solvent is 3 to 10 times the mass of the PVDF; the organic solvent is N,N-dimethylformamide; the mass of the PVDF is 3 to 6 times the mass of the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane; the lithium salt is lithium bis(trifluoromethanesulfonylimide); the mass of the lithium salt is 2 to 5 times the mass of the succinate; the mass of the succinate is equal to the mass of the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane; in some specific embodiments, the PVDF is HSV900 or 5130.

[0029] The pretreatment solution of the composite polymer electrolyte is coated into a film by scraping and then dried to obtain the nano-silica composite polymer electrolyte; the drying temperature is 70-80℃.

[0030] A method for preparing a nano-silica composite polymer electrolyte is provided, comprising blending a trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate with polyvinylidene fluoride (PVDF) to obtain a pre-solution of the composite polymer electrolyte. The resulting composite polymer electrolyte has a highly compatible polymer / filler interface, enabling the preparation of a battery with high interfacial compatibility and long-cycle charge-discharge stability.

[0031] The hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane, when blended with polyvinylidene fluoride (PVDF), achieves uniform dispersion of monodisperse silica within PVDF. Simultaneously, the long fluorocarbon chains formed by the 3,3,4,4,5,5,6,6,6-nonafluorohexyl groups in the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane interact with PVDF, exhibiting high compatibility and enhancing the hydrophobicity and thermal stability of the electrolyte. Furthermore, the overall interaction between the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate and the matrix material improves the electrochemical performance of the battery.

[0032] In some embodiments, the method for obtaining a hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane includes: adding ammonia to trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane, and magnetically stirring at a temperature of 70–90°C for 8–12 h to obtain a hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane; wherein the mass of the ammonia is 2–6 times the mass of the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane, and the mass percentage concentration of the ammonia is 25%;

[0033] By directly adding ammonia to trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane and then hydrolyzing it under magnetic stirring at 70–90 °C, the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane is fully hydrolyzed. The hydrolysis is complete, with no byproducts such as hydrogen chloride generated. The resulting monodisperse SiO2 and long fluorocarbon chains that can bind to PVDF effectively prevent SiO2 aggregation during subsequent reactions with PVDF. This achieves high dispersion of silica particles in PVDF and functional modification of PVDF by the long fluorocarbon chains, resulting in a composite polymer electrolyte with high interfacial compatibility.

[0034] In some embodiments, the method for obtaining a pre-solution of the composite polymer electrolyte includes:

[0035] Polyvinylidene fluoride and an organic solvent were added to the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate, and the mixture was stirred at 70-90°C to obtain a mixed system.

[0036] Succinate and lithium salt were added to the mixture and stirred at 70–90°C to obtain a pre-solution of the composite polymer electrolyte.

[0037] Furthermore, by sequentially adding PVDF and lithium salt to the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate, and utilizing the ammonia in the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate system, the defluorination of PVDF, lithium salt dissociation, long fluorocarbon chain modification, and dispersion of monodisperse silica in the matrix are simultaneously achieved. This further improves the interfacial compatibility between the composite PVDF polymer electrolyte and the lithium metal anode, enabling efficient lithium ion transport during discharge. Under conditions of a polarization voltage of 10 mV and a polarization time of 2000 s, the room temperature lithium ion transference number of the lithium symmetric battery is 0.6.

[0038] On the other hand, a nano-silica composite polymer electrolyte prepared by the above method is provided.

[0039] On the other hand, a full battery comprising the above-mentioned nano-silica composite polymer electrolyte is provided, comprising: a lithium iron phosphate cathode, the above-mentioned nano-silica composite polymer electrolyte, and a lithium sheet.

[0040] Furthermore, a method for assembling a full battery using the aforementioned nano-silica composite polymer electrolyte as the electrolyte is also provided, comprising:

[0041] Step 1: Transfer the nano-silica composite polymer electrolyte to a glove box and cut it using a punching machine to obtain a thin film;

[0042] Step 2: Assemble the thin film with the lithium iron phosphate cathode and lithium sheet to obtain a full cell.

[0043] In some embodiments, the method for preparing the lithium iron phosphate cathode includes:

[0044] Step 201: Mix lithium iron phosphate powder, polyvinylidene fluoride, conductive carbon black and N-methylpyrrolidone in a mass ratio of 8:1:1:40 to obtain lithium iron phosphate pretreatment solution; in some specific embodiments, the conductive carbon black is Ketjen black.

[0045] Step 202: The lithium iron phosphate pretreatment solution is coated into a film to obtain a lithium iron phosphate positive electrode sheet.

[0046] Prior to this application, a series of experiments were conducted. Some of the experimental results are listed below to provide a more detailed description of the invention. The following is a detailed description in conjunction with the embodiments.

[0047] In the following embodiments, the raw materials and structural formulas are shown in Table 1. The present invention does not specifically limit the source of each raw material. Unless otherwise specified, they are all commercially available or synthesized by ourselves.

[0048] Table 1 shows the raw materials and structural formulas in the embodiments.

[0049]

[0050]

[0051] Example 1

[0052] This embodiment provides a method for preparing a nano-silica composite polymer electrolyte, including the following steps:

[0053] Step 1: Provide a hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane: Add 0.8g of ammonia to 0.2g of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane (FSCA) to adjust the pH to alkaline. Stir the system magnetically for 8 hours at 80°C to obtain the hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane; the ammonia concentration is 25% by mass.

[0054] Step 2: Add 1g of polyvinylidene fluoride (PVDF) and 10g of organic solvent N,N-dimethylformamide (DMF) to the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate. Continue heating and stirring overnight at 80°C to obtain a mixed system. The polyvinylidene fluoride (PVDF) is HSV900, purchased from KELOUDE.

[0055] Step 3: Add 0.2g of succinate (SN) and 0.4g of lithium salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to the mixture, and continue heating and stirring at 80°C to mix evenly, to obtain the pre-solution of composite polymer electrolyte.

[0056] Step 4: The pretreatment solution of the composite polymer electrolyte is evenly scraped onto a clean glass plate, and then the glass plate is placed in a 70°C oven to dry for 24 hours to remove the organic solvent, thus obtaining the nano-silica composite polymer electrolyte, named CPE-PVDF|FSCA.

[0057] This embodiment also provides a method for assembling a full battery using the above-mentioned nano-silica composite polymer electrolyte as the electrolyte, including:

[0058] Step 1: Transfer the nano-silica composite polymer electrolyte to a glove box, cut it using a die-cutting machine to obtain a thin film, and drop 5 microliters of fluoroethylene carbonate onto the surface of a 14mm diameter lithium sheet, mixing it with the thin film and the lithium iron phosphate positive electrode sheet according to... Figure 1 Assembly yields a coin cell CR2032; the diameter of the thin film is 16mm or 18mm; the preparation method of the lithium iron phosphate cathode includes:

[0059] Step 101: Mix lithium iron phosphate powder, PVDF, Ketjen black and N-methylpyrrolidone (NMP) in a mass ratio of 8:1:1:40 to obtain lithium iron phosphate pretreatment solution; the Ketjen black is model Ketjen black ECP-600JD, purchased from KELU.

[0060] Step 102: According to the coating surface density of 2.5 mg / cm³ 2 The lithium iron phosphate pretreatment solution is evenly coated onto carbon-coated aluminum foil using a scraper, and then dried in a 70°C oven for 24 hours to remove the organic solvent. The foil is then cut using a die-cutting machine to obtain a circular sheet with a diameter of 12 mm, which is the lithium iron phosphate positive electrode sheet.

[0061] Comparative Example 1

[0062] This comparative example investigates the effect of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane on the performance of the composite polymer electrolyte. The method for preparing the composite polymer electrolyte is the same as in Example 1, except that:

[0063] Step 1: Add 10g of N,N-dimethylformamide to 0.2g of silica powder with a particle size of 2 micrometers, and stir magnetically for 8h at 80℃ to obtain a silica-containing system.

[0064] Step 2: Add 1g of polyvinylidene fluoride to the silica-containing system, and continue heating and stirring overnight at 80°C to obtain a mixed system; the polyvinylidene fluoride is the same as in Example 1.

[0065] The electrolyte obtained in this comparative example is named CPE-PVDF|SiO2.

[0066] The method for obtaining the composite polymer electrolyte and the method for assembling the full cell in this comparative example are basically the same as those in Example 1. The schematic diagram of the assembled full cell structure is shown below. Figure 2 As shown.

[0067] Performance Evaluation

[0068] 1. Long-cycle testing

[0069] The coulombic efficiency of the full cells of Example 1 and Comparative Example 1 was tested at room temperature and 0.5C rate. The results are as follows: Figure 3 As shown. According to Figure 3 As can be seen, the full cell assembled with CPE-PVDF|SiO2 with a diameter of 16 mm in Comparative Example 1 showed a significant decrease in coulombic efficiency after 100 cycles. The full cell assembled with CPE-PVDF|FSCA with a diameter of 16 mm in Example 1 still maintained 100% coulombic efficiency after 200 cycles and could still maintain a capacity of close to 150 mAh / g after 200 cycles, showing high long-cycle capacity retention and stable charge-discharge cycle performance.

[0070] 2. Room temperature ionic conductivity test

[0071] The 16mm diameter composite polymer electrolyte CPE-PVDF|FSCA from Example 1 was sandwiched between two stainless steel pads to assemble an SS / SS coin cell. The method for assembling the composite polymer electrolyte in Comparative Example 1 to obtain an SS / SS coin cell was the same as described above. Tests were performed using an electrochemical workstation at frequencies ranging from 0.1 to 10 Hz. 6 Hz, test results are as follows Figure 4 As shown, the ionic conductivity (σ) is calculated using the following formula:

[0072]

[0073] Where σ is the ionic conductivity, with units of S cm. -1 L is the electrolyte membrane thickness in cm; R is the impedance at room temperature in Ω; S is the area of ​​the stainless steel gasket in cm². 2 ;

[0074] Combination Figure 4 It can be seen that the room temperature ionic conductivity of the stainless steel coin cell assembled by CPE-PVDF|FSCA in Example 1 is 2.74 × 10⁻⁶. -4 S cm -1 The stainless steel coin cell assembled with CPE-PVDF|SiO2 in Comparative Example 1 has a room temperature ionic conductivity of 2.12 × 10⁻⁶. -4 S cm -1 .

[0075] 3. Room temperature ion transport number test

[0076] A (Li / Li) symmetrical battery was formed by sandwiching a 16mm diameter CPE-PVDF|FSCA wafer between two 14mm diameter lithium wafers. The assembly method for the (Li / Li) symmetrical battery using CPE-PVDF|SiO2 in Comparative Example 1 was the same. Constant voltage polarization and EIS tests were performed using a Chenhua CHI760E electrochemical workstation. The polarization time was 2000s, and the polarization voltage was 10mV. The lithium-ion transport number t of the electrolyte was calculated using the formula. Li + :

[0077] Where ΔV is the polarization voltage in millivolts; I0 is the initial polarization current in microvolts.

[0078]

[0079] An;I S R0 is the steady-state current after polarization, in microamps; R0 is the resistance before polarization, in ohms; R0 S The resistance after polarization is expressed in ohms.

[0080] The test and calculation results of ion transport numbers are as follows: Figure 5 As shown, according to Figure 5 As can be seen, the ion transference number of the CPE-PVDF|FSCA assembled battery in the embodiment of the present invention is 0.60, which is greater than that of the comparative CPE-PVDF|SiO2 assembled battery (0.54), confirming that the silica composite polymer electrolyte of the present invention can effectively promote the migration of lithium ions.

[0081] 4. SEM testing

[0082] The microstructure of the composite polymeric electrolyte was observed using cold field emission scanning electron microscopy (SEM). The testing method included: attaching conductive adhesive to the sample stage, adhering the CPE-PVDF|FSCA from Example 1 to the conductive adhesive, vacuum drying overnight at 60°C, and performing two gold sputtering treatments using Pt as the target material. The sputtering current was 10 mA, and the sputtering time was 50 s each time. The treatment method for CPE-PVDF|SiO2 in Comparative Example 1 was the same as described above. The results are as follows: Figure 6 and Figure 7 As shown, where Figure 6 This is a SEM image of the composite polymer electrolyte CPE-PVDF|FSCA from Example 1. Figure 7 This is a SEM image of the composite polymer electrolyte CPE-PVDF|SiO2 from Comparative Example 1. Based on... Figure 6 and Figure 7 As can be seen, the CPE-PVDF|SiO2 composite polymer electrolyte of Comparative Example 1 showed obvious particle agglomeration and pores under SEM, with a high pore content. The CPE-PVDF|FSCA composite polymer electrolyte of Example 1 was uniform, compact, smooth, and without obvious pores, indicating that the method of the present invention can obtain nano-silica composite polymer electrolyte with high interfacial compatibility.

[0083] 5. Battery performance stability in complex application scenarios

[0084] Using the composite polymer electrolyte CPE-PVDF|FSCA from Example 1 as the electrolyte membrane, a soft-pack battery was assembled. The assembly method included: cutting CPE-PVDF|FSCA into squares and assembling them with lithium sheets containing added fluoroethylene carbonate and lithium iron phosphate positive electrode sheets; connecting the positive aluminum tabs and negative nickel tabs to the electrode sheets by welding; sealing with an aluminum-plastic film; performing an initial charge to activate the electrodes and form an SEI film; removing gas and residual electrolyte; and resealing to obtain the soft-pack battery. The coating surface density during the preparation of the lithium iron phosphate positive electrode sheet was 7.5 mg / cm². 2 A physical demonstration diagram of the pouch battery driving external components is shown below. Figure 8 As shown, the soft-pack battery of the present invention can drive an external load and has stable discharge performance. Lateral folding, longitudinal folding and partial cutting do not significantly affect the discharge performance.

Claims

1. A method for preparing a nano-silica composite polymer electrolyte with high interfacial compatibility, characterized in that, include: A method for providing a hydrolysate of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane includes: adding ammonia to trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane, and magnetically stirring at 70-90°C for 8-12 hours to obtain the hydrolysate; wherein the mass of the ammonia is 2-6 times the mass of the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane, and the mass percentage concentration of the ammonia is 25%; Polyvinylidene fluoride and an organic solvent were added to the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate, followed by the addition of succinate and lithium salt to obtain a pre-solution of the composite polymer electrolyte. The pre-solution of the composite polymer electrolyte is coated into a film by scraping and drying to obtain a nano-silica composite polymer electrolyte with high interfacial compatibility.

2. The method for preparing the high interfacial compatibility nano-silica composite polymer electrolyte according to claim 1, characterized in that, include: The mass of the polyvinylidene fluoride is 3 to 6 times the mass of trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane; and / or, the mass of the organic solvent is 3 to 10 times the mass of the polyvinylidene fluoride; and / or, the mass of the lithium salt is 2 to 5 times the mass of succinic anionyl nitrile.

3. The method for preparing the high interfacial compatibility nano-silica composite polymer electrolyte according to claim 1, characterized in that, The drying temperature is 70~80℃.

4. The method for preparing the high interfacial compatibility nano-silica composite polymer electrolyte according to claim 1, characterized in that, Methods for obtaining a pre-solution of the composite polymer electrolyte include: Polyvinylidene fluoride and an organic solvent were added to the trimethoxy(3,3,4,4,5,5,6,6,6-nonafluorohexyl)silane hydrolysate, and the mixture was stirred at 70~90℃ to obtain a mixed system. Succinate and lithium salt were added to the mixture and stirred at 70-90°C to obtain a pre-solution of the composite polymer electrolyte.

5. A nano-silica composite polymer electrolyte obtained by the preparation method of the high interfacial compatibility nano-silica composite polymer electrolyte as described in claim 1.

6. A full battery comprising the nano-silica composite polymer electrolyte as described in claim 5, characterized in that, include: The lithium iron phosphate cathode, the nano-silica composite polymer electrolyte, and the lithium sheet.

7. A method for assembling a full battery as described in claim 6, characterized in that, include: Step 1: Transfer the nano-silica composite polymer electrolyte to a glove box and cut it using a punching machine to obtain a thin film; Step 2: Assemble the thin film with the lithium iron phosphate cathode and lithium sheet to obtain a full cell.

8. The method according to claim 7, characterized in that, The method for preparing the lithium iron phosphate cathode includes: Step 201: Mix lithium iron phosphate powder, polyvinylidene fluoride, conductive carbon black and N-methylpyrrolidone in a mass ratio of 8:1:1:40 to obtain lithium iron phosphate pretreatment solution. Step 202: The lithium iron phosphate pretreatment solution is coated into a film to obtain a lithium iron phosphate positive electrode sheet.

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